Its spring, which means it’s the season for fresh, juicy berries. And that’s good news for your brain.

Researchers report in the journal Annals of Neurology that women who ate berries more frequently over a period of years showed slower decline in brain functions such as memory and attention when they got older than women who ate them less often. The findings don’t confirm that eating berries can prevent dementia associated with aging, or slow down Alzheimer’s, but they suggest that the fruits may play a part in keeping brains healthy.

The protective effect of blueberries and strawberries isn’t an entirely new finding. But previous studies have involved animals and only a small number of people, which left open the possibility that it wasn’t the berries, but something else that might be influencing how quickly the brain lost its executive functions.

In the current analysis, Elizabeth Devore, an instructor in medicine at Brigham and Women’s Hospital, and her colleagues addressed the gap in the research by reviewing the eating habits of a single cohort of 16,000 women participating in the Nurses Health Study. During their 50s and 60s, every four years the women answered questions by phone about what they ate. And in their 70s, they came into the lab for six different cognitive function tests. Devore and her team also had information on the women’s education, income and other socioeconomic factors that can affect cognitive function.

Their findings confirmed that women who ate berries at least once a week were able to slow down their cognitive decline by about 1.5 to 2.5 years. For blueberries, the effect started with about a half cup of berries each week; for strawberries, it took about a cup of the fruit per week. This effect persisted even after the scientists accounted for the fact that berry-eaters might also have other brain-healthy habits or characteristics, such as having more education and engaging in intellectually satisfying pursuits such as learning new languages or maintaining a rich network of social connections. “In the end, we did not see a lot of confounding from these factors,” says Devore.

She and her colleagues focused their attention on berries because rodent studies showed that the key compound in berries, a flavonoid called anthocyanidin, could seep through the blood and into brain tissues — specifically concentrating in the hippocampus, which is responsible for learning and memory. As an antioxidant, flavonoids also fight inflammation and oxidation, both processes that affect aging brain cells.

The study is only the first to track berry consumption long term until cognitive decline set in, and the findings will need to be repeated and confirmed. But in the meantime, says Devore, it makes sense to add blueberries and strawberries to your diet, frozen or fresh. “I don’t think there are many downsides to that. The availability of berries and access to this kind of intervention is great as a public health message.” And a tasty one too.